The invention relates to a thermostable melt of polyurethane and/or polyurethane urea elastomer, which can be handled and processed over a long period of time or which, after cooling, can be remelted and thermoplastically processed to shaped articles, such as fibers, threads, flat and molded bodies, or can be used as a hot-melt adhesive.
The invention also relates to a process for producing the melt.
Polyurethane and polyurethane urea elastomers are among the materials which are obtained by means of special production technologies, such as stepwise dosing in a screw machine (DE-OS 28 42 806), reactive injection molding (RIM) processes (EP 81 701), or production and processing in solution (U.S. Pat. Nos. 3,557,044, 3,565,894, 3,721,656).
Whereas thermoplastic polyurethanes can be processed in the melt without significant deterioration of the material characteristics, thermoplastic polyurethane urea elastomers after synthesis cannot be kept in the melt or remelted again. The reason is that the melting point of the polyurethane urea compound is above the decomposition temperature (Kolloid-Z and Z. Polymere, 241, 1970, pp. 909-915).
One important field of use of polyurethane and polyurethane urea elastomers is, for example, that of elastomeric fibers. Polyurethane urea elastomeric fibers are largely produced by dry or wet spinning processes. The melt spinning process is used for special modifications of PU-silk (Encyclopedia of Polymer Science and Engineering, vol. 6, 733, 1986, J. Wiley Interscience). Processes are known for producing elastomer threads by the much less expensive melt spinning technology.
The market leaders are polyurethane urea elastomeric fibers produced by means of solvent, i.e. dry or wet spinning processes, because polyurethane urea elastomers, after synthesis, cannot be kept in the melt or remelted again.
There is consequently a considerable need to make available a processable melt from polyurethane and/or polyurethane urea elastomer which can be processed over a longer synthesis and processing period. It is important for the melt to be handlable without domain formation/phase separation up to the processing to shaped articles or as a hot-melt adhesive or, after cooling and without any deterioration in the material data, can be remelted and processed.
The problem of the present invention is to provide a novel polyurethane and/or polyurethane urea elastomer which allows a problem-free processing of the elastomer to shaped or molded articles, while avoiding the expensive RIM technology or the production and processing of the elastomers in solution with a subsequently costly solvent recovery and disposal.
A process for producing the polyurethane and/or polyurethane urea elastomers is also to be provided.